I'm reporting this bug on behalf of someone who does not have a forum account of their own.
After looting the "Rift Treasure Map, Scrivener's Treasure" in Scrivener's Hall on PC/NA on March 15...

And then digging this treasure map up, the associated achievement, "Missing Map Recovered" remains unearned...

This also means that the associated tool, the Cartoklept Map, cannot be obtained.
The following are my own personal comments on this bug:
I know that this was working last patch, since I was able to get this achievement on one of my alt accounts on PC/EU during U48:
My best guess is that since this is a special treasure map, and there were changes made to how treasure maps behave in Update 49, that these changes somehow affected the conditions that are supposed to trigger the achievement.
Nightfighters ― PC/NA and PC/EU
Dungeons and Trials:
Personal best scores:
- Dragonstar Arena: 46817 (NA)
- Maelstrom Arena: 600526 (NA)
- Blackrose Prison: 99274 (EU) (Unchained)
- Maw of Lorkhaj: 165227 (EU)
- Halls of Fabrication: 220708 (NA) (Tick-Tock Tormentor #1, #2, #3, #4, #5, #6, #7, #8, #9, #10, #11, #12)
- Asylum Sanctorium: 114957 (NA) (Immortal Redeemer #1, #2, #3, #4, #5, #6, #7, #8, #9, #10)
- Cloudrest: 131256 (NA) (Gryphon Heart #1, #2, #3, #4, #5, #6, #7)
- Sunspire: 250866 (EU) (Godslayer #1, #2, #3, #4, #5, #6, #7)
- Kyne's Aegis: 235841 (EU) (Dawnbringer #1, #2, #3, #4, #5, #6, #7, #8)
Dungeon trifectas: